1. Field of the Invention
This invention relates to the field of ignition systems for internal combustion engines, and in particular to an improved electronic ignition system that replaces breaker point type ignition systems and less capable ignition systems.
2. Brief Description of the Prior Art
Electronic distributor ignition systems for replacement of point type distributors are well known in the art. Basically, such electronic ignition systems receive their timing information from the distributor camshaft and convert the changing angular position of the camshaft into a series of pulses for ultimately creating a spark for distribution to the spark plugs in a timed relationship to the rotation of the distributor camshaft. Several electronic ignition systems of the prior art modulate a source of either magnetic or optical flux. A sensor within the engine distributor housing monitors the modulated signal. Electronics associated with the sensor detects the modulated signal, then generates and transmits a trigger signal for the spark. Synchronization of the modulation source with the position of distributor camshaft sets the timing of the spark.
The use of Hall-effect devices in electronic ignition systems is also known in the art. In some cases, a single magnet and a single Hall-effect device are spaced apart, and a rotatable object timed with the camshaft passes through the magnetic flux between the magnet and the Hall-effect device, inducing an output from the Hall-effect device. In other arrangements, a pair of magnets with a single Hall-effect device between them, or a pair of Hall-effect devices with a single magnet between them, are employed, but the same technology is relied upon, i.e. producing spark timing pulses by the passing of a rotatable disc-like object, or objects, within the magnetic field, or fields, standing between the magnet(s) and Hall-effect device(s).
One such prior art device can be found in U.S. Pat. No. 5,406,926 to Huan-Lung Gu. This reference shows, in one embodiment, a spark ignition system for an internal combustion engine having a radially extending vane mounted on the distributor rotor shaft and rotates therewith. The vane, at its radially outer end has an axially extending portion which passes by a Hall-effect sensor. The number of axially extending portions is the same as the number of cylinders. The distributor rotor is also mounted on the shaft and is spaced from the vane. An integral part of the apparatus is a stray noise isolating plate (10) extending across the distributor and separating the rotor from the vane. As the shaft rotates, a signal is generated to initiate the spark. Other embodiments have multiple vanes for generating additional signals used for other engine functions. Another embodiment shows a distributorless system with a plurality of coils. There is no distributor rotor, but the top of the unit is closed by the stray noise isolating plate. In some embodiments, the second vane is asymmetrical and provides a signal for fuel injection. While not specifically called out, the structure shown seems to indicate that the axially extending portion passes between the Hall-effect unit and a magnet.
U.S. Pat. No. 5,158,056 to Raymond King shows an ignition system for a spark ignition engine in which a hub is mounted on the camshaft and has a plurality of magnets mounted on the periphery of the hub. A stationary magnetic sensor detects each magnet as it passes during each rotation and generates the signal for the spark ignition.
U.S. Pat. No. 5,127,387 to Haruyuki Matsuo shows a spark ignition signal generator in which a radially extending plate is mounted on a shaft rotated by the engine. At the radially outer end of the plate are tabs bent to be axially oriented. A stationary magnet is positioned in spaced relationship to the Hall-effect unit and the tabs pass between the Hall-effect unit and the magnet on each rotation. The apparatus is directed to the particular shape of the plate.
U.S. Pat. No. 5,126,663 to Izuru Shinjo shows the detailed design for a particular type of mounting for a Hall-effect unit in which a spring type arm provides a resilient force to the plate on which the Hall-effect unit is mounted, allegedly eliminating distortion to the Hall-effect unit.
U.S. Pat. No. 5,097,209 to Alfred J. Santos shows a spark ignition system for an internal combustion engine. A plate is mounted around the shaft of the distributor and extends radially outward. A pair of rings are on the plate, and each mounts a plurality of magnets in spaced apart relationship. Hall-effect units are fixed in place and detect the passage of the magnets. Two Hall-effect units are used to detect the outer ring of magnets to provide two signals for each passing magnet. A single Hall-effect unit detects the inner magnets as they pass to provide a single signal. The signals are used to initiate the spark.
U.S. Pat. No. 5,093,617 to Shigemi Murata shows various arrangements of a Hall-effect unit as used in an ignition timing system for internal combustion engines. In the first embodiment, a toothed wheel passes by a front surface of a Hall-effect sensor unit, and the magnet is mounted behind the back surface of the Hall-effect unit. Rotation of the toothed wheel is synchronous with the engine. In all the other embodiments, the toothed wheel passes between the magnet and the Hall-effect unit. The signal generated is used to control engine functions.
U.S. Pat. No. 5,028,868 to Murata et al. shows a flux shutter which is similar to the vane of the aforementioned ""926 patent and which passes between the magnet and the Hall-effect unit to generate an engine signal for ignition timing control. In all embodiments, the axial portion of the vane passes between the magnet and the Hall-effect unit. Several different mounting arrangements for the Hall-effect unit and magnet are shown.
U.S. Pat. No. 4,901,704 to Edward J. Safranek reference shows an engine ignition timing structure in which a plurality of magnets are positioned on the outer rim of the flywheel of an engine and rotate therewith. A stator assembly has the coils and four Hall-effect units mounted thereon to sense the passage of the axial portions 6 and 7 of the flux concentrators 29a and 29b which rotate with the flywheel along with a ring magnet 28 which is spaced from the fixed Hall-effect units. The signal generated by the Hall-effect units is used for ignition timing through a circuitry designed to eliminate the dependency of ignition timing on engine RPM.
U.S. Pat. Nos. 4,508,092 and 4,406,272 to Kiess et al. show a distributorless ignition system in which, in one embodiment, a single Hall-effect unit is positioned between two magnets in a spaced apart relationship radially outward from a rotating shaft. A disc is connected to the crank shaft of the engine for rotation with the shaft, and axially extending flange like members at different radial positions pass through the gaps formed between the magnets and the Hall-effect units. This sequentially generates two signals from the Hall-effect unit, one positive and one negative. These signals are processed through differential amplifiers and Schmidt triggers to a micro processor which utilizes the positive signal for operation of the spark in cylinders 1 and 4 and the negative signal for operation of the spark in cylinders 2 an 3. In a second embodiment, there are provided two Hall-effect units with a spaced magnet between them. The same type of flanges move between the magnet and the Hall-effect units to provide the two output signals. A third embodiment is similar to the first and is linearly arranged for detecting linear motion.
U.S. Pat. No. 4,224,917 to Nakazawa et al. concerns the known idea of using a signal pickup device, amplifying the signal that is picked up, and transmitting the amplified signal to an ignition coil. Magnetic poles 5 are situated opposite the rotor tips and sense the passing of the rotor tips. The alleged new features are the placement of the amplifier circuit, or the amplifier circuit and output transistor in a waterproof housing on the outside of the distributor housing.
U.S. Pat. No. 4,235,213 to Jellissen concerns the known idea of using a signal pickup device for providing timing signals for an engine ignition distributor system. The apparatus uses a modified rotor assembly 20 having downwardly extending ferrous vanes for passing through the gap of a Hall Effect device.
U.S. Pat. No. 4,365,609 to Toyama et al. concerns the known idea of using a signal pickup device, amplifying the signal picked up, and transmitting the amplified signal to an ignition coil. An electromagnetic pickup 2 is situated opposite the rotor tips and senses the passing of the rotor tips. The main features of the apparatus according to this patent are the provision of an ignition coil in the distributor and the orienting of the magnetic field of the ignition coil relative to the magnetic detector to minimize erroneous ignition timing.
U.S. Pat. No. 4,499,888 to Hino et al. uses a coil/core-sensor to detect a rotating xe2x80x9csignal rotor 1axe2x80x9d and employs resonant circuit technology. A simple routing arrangement is used for sending the sensed signal from an oscillatory signal generator unit 1, through an amplifier and on to the ignition coil
U.S. Pat. No. 5,058,559 to Koiwa discloses a means for developing an ignition timing signal which is applied to an ignition coil via a simple amplifier circuit shown in FIG. 4. The signal pickup 14 is not well defined, and no rotating magnets are suggested.
In U.S. Pat. No. 5,076,249 to Ikeuchi et al., the signal pickup and routing is similar to that of Koiwa described above, except that the Ikeuchi apparatus uses light sensing techniques to determine shaft angular position. There is no suggestion to use moving magnets.
U.S. Pat. No. 5,365,909 to Sawazaki et al. proposes the use of a pair of disc plates each having folded portions passing through the gap of a Hall Effect device. The reference does not suggest rotating magnets, and no signal processing function is suggested.
All of the devices and apparatuses of the prior art, in the implementation of an electronic ignition system, have one or more shortcomings. Specifically, many prior art devices require a completely new mechanical design for the distributor, and therefore cannot be adapted to fit existing engines without great expense. Additionally, especially for owners of vintage automobiles or boats, the owners do not want to replace genuine distributors with non-genuine ones. They would reject to notion of improving engine performance if it meant that the engine would not retain its original visual characteristics and charm.
Yet, it is recognized by those skilled in the art that precise timing and dwell period of an engine is critical to its performance. Using the electronic ignition systems of the prior art, while timing may be precisely set, it can vary substantially from the preset condition upon the degradation of components, tolerance of parts, variation of battery power due to discharging and charging cycles, variation of the trigger point in the circuitry receiving the output from the sensor, imprecise threshold detection of analog waveforms having inherently wide range detection windows, and other similar factors.
There is a need in the art for an improved electronic ignition system which has more accurate and stable timing and dwell characteristics, substantially independent of aging of parts, power variations, and critical threshold requirements, and which can be designed to produce precise timing and dwell parameters applicable to a variety of different engines and/or engine types.
In addition, there is a need in the art to dynamically alter timing and dwell parameters in real time. In this connection, there is a need to automatically alter timing and dwell parameters differently when the engine is starting than when it is running, as well as when the engine transitions from starting to running. Dynamic performance regulation and correction requires a close monitoring of changing engine parameters such as engine RPM. The present invention satisfies these needs and more.
In describing the operation of the invention, certain mechanical and functional features and relationships will be defined and explained. The following definitions will assist in understanding the terms used herein.
Camshaft axis is the longitudinal axis of the camshaft, more generally referred to herein as a xe2x80x9crotary shaftxe2x80x9d, of a distributor for an internal combustion engine. A typical camshaft has radially projecting lobes, and is described herein as rotating clockwise or counterclockwise as the camshaft would be viewed from above, i.e. as it would be observed from the top of the distributor.
Camshaft rotational direction refers to the clockwise or counterclockwise rotational movement of the distributor camshaft as viewed from above, i.e. as it would be observed from the top of the distributor. Dwell period and timing are both affected by the rotational direction of the camshaft for a given sensor arrangement.
Timing refers to the time coincidence of a spark generated by the ignition system and the position of a piston as determined by the angular position of the camshaft driven in synchronism with the crankshaft of an engine.
Dwell refers to the portion of the timing cycle between spark generations in which current builds up in the primary of the ignition coil.
It is to be noted that the dwell period is vital to the performance of all induction ignition systems. It is during this period that current in the primary of the ignition coil increases. The current that is flowing in the primary at the time of the spark and the inductance of the primary are the key parameters that determine the energy available for the spark. The energy available for spark generation determines the available voltage for the spark and the spark duration. Both voltage and spark duration are essential to reliable ignition of the fuel-air mixture. Thus, the importance of the dwell period cannot be overstated.
In the description to follow, it will be assumed that the camshaft sensing arrangement may be constructed from discrete functional components, or it may include a Hall-effect integrated circuit (HEIC). A technical description of the operation of an HEIC as a gearwheel tooth speed and position indicator is presented in an article by Klaus Fischer entitled Dynamic differential all-effect ICs measure speed, position and angle in a publication xe2x80x9cAPPLICATIONSxe2x80x94AUTOMOTIVE ELECTRONICSxe2x80x9d (1997) No. 4, such publication being incorporated herein by reference.
An improved electronic ignition arrangement for an internal combustion engine having an output drive shaft, a rotary shaft coupled to the output drive shaft, a plurality of spark plugs, an ignition coil, and a rotor and distributor arrangement to effect sequential firing of the spark plugs, the rotor coupled to the rotary shaft for rotation therewith, the ignition system arrangement producing a software modifiable control signal routed to the ignition coil to effect sequential firing conditions for the ignition coil and spark plugs and thereby improving performance of the engine.
The principles of the present invention can be applied during the design of a new engine and freely manufactured to mechanical engineering specifications at the discretion of the manufacturer or designer. However, the invention will have major application in retrofitting older engines by directly replacing older breaker point type ignitions systems, or by directly replacing certain prior art electronic ignition system arrangements, with a new and improved one, without any redesign or mechanical alterations to the engine or distributor, and without altering the visual aspects of the engine or distributor.
The operating parts of the invention fit under the original or stock distributor cap and has only two wires to hook up. Available as a kit of parts, the invention can be installed easier and more conveniently within the existing distributor of an engine than a set of breaker points and condenser. Being modular and with all electronics encased in a sealed ignitor module housing, the present invention is not affected by dirt and dust and is virtually waterproof. Due to the intelligent microprocessor based controller in the ignitor module, shifts due to points wear, condenser or points failure, and periodic replacement of points are non-existent considerations. Moreover, with close and continuous monitoring of certain engine parameters, the present invention provides consistency in engine performance, improved fuel mileage, positive starting, and longer plug life.
In one aspect of the invention, there is provided an ignition arrangement for analyzing a selected operating condition of an internal combustion engine, and making an adjustment to a designated engine parameter associated with the selected operating condition, in accordance with predetermined specifications.
As non-limiting examples: when the selected operating condition is engine starting, that is, when the engine is making the transition from the crankshaft in a non-rotating condition thereof to the crankshaft in a rotating condition thereof under the power of the electrically powered starter driven by the battery the adjustment increases dwell period; when the selected operating condition is engine running, that is, when the engine is rotating the crankshaft under its own power the adjustment decreases dwell period; when the selected operating condition is the value of ignition coil current lower than a preset value just before spark, the adjustment increases dwell period; when the selected operating condition is the value of ignition coil current greater than a preset value just before spark the adjustment decreases dwell period; when the selected operating condition is the sensed RPM greater than a preset value, the adjustment increases advance; when the selected operating condition is engine not turning over, the adjustment terminates dwell mode, reinitializes all starting parameters, and waits for a power-on reset; when the selected operating condition is engine running, and ignition coil current is lower than a preset value, the adjustment increases dwell period; and when the selected operating condition is engine running, and ignition coil current is higher than a preset value, the adjustment decreases dwell period.
In adapting the invention to existing engines with breaker point type distributors, in one aspect of the invention, the ignition system arrangement comprises a magnet carrier mountable on the rotary shaft for rotation therewith, the carrier having a plurality of magnetic regions spaced about the periphery of the rotary shaft, a sensor positionable in close proximity to ones of the plurality of magnetic regions as the magnet carrier rotates, the sensor producing a sensor output signal representing the passing of each magnetic region by the sensor, and an ignitor module, responsive to receiving the sensor output signal, for producing the control signal and making it available to the ignition coil.
In a preferred embodiment of the invention, the magnet carrier is an annular ring insertable over the rotary shaft and adapted to be fixed to the underside of the rotor. In an alternative version, the magnet carrier comprises an annular sleeve adapted to fit over the lobe member fixed to the rotary shaft beneath the rotor (e.g., over the lobe member of the crankshaft).
In another aspect of the invention, there is provided an improved ignition arrangement for an internal combustion engine comprising an apparatus for producing a series of electrical pulses in synchronism with the rotary shaft sequentially rotating through predetermined angles of rotation, and an ignitor module, responsive to receiving the series of electrical pulses, for exciting the ignition coil at the end of each dwell period, the ignitor module comprising a processor for analyzing the series of electrical pulses to determine when the engine is starting and when it is running, and for altering the dwell period responsive to such determination.
An additional, or alternative, function of the ignitor module is to increase the dwell period when the processor determines that the engine is starting and to decrease the dwell period when the processor determines that the engine is running.
In another aspect of the invention, the ignitor module is adapted to monitor the ignition coil current just prior to generating a spark, and to adjust the dwell accordingly for optimum operating efficiency and spark energy.
In another aspect of the invention, the ignitor module is adapted to dynamically adjust the dwell only to a period sufficiently long that the peak current level is reached just before the dwell period ends, thereby providing constant spark energy over the RPM range of the engine.